The present invention relates to a memory device composed of semiconductor elements and, more particularly, to a refreshing system for a dynamic type memory device using insulated-gate field-effect transisitors.
Dynamic type random access memories (hereinafter referred to as RAMs) are widely used in many fields. Recently, a RAM designated "MK 4816" and employing an improved refresing system was announced by MOSTEK co. of U.S.A. The latter device allows an internal refresh in which a refresh operation for memory cells is internally performed without receiving any refresh address information from the outside thereof by using a refresh control signal in addition to the conventional external refresh which requires refresh address information from the outside. This RAM achieves high-flexibility in control and its application.
RAMs employing multi-address input system in which row address information and column address information are incorporated respectively synchronism with row address strobe signal RAS and column address strobe singal CAS are substantially standard for dynamic RAMs with large capacity. A multi-address input type RAM is disclosed in U.S. Pat. No. 3,969,706 issued to R. J. Proebsting et al.
However, the multi-address input type RAM has some limitations between the strobe signals and the refresh operation, and such limitations have prevented the multi-address type RAM from incorporating the internal refresh of the "MK 4816" therein.